That's not a very common use case for C, either now or back then (arguably you probably had more user-facing C cgi back then, but it was still one invocation per user so arguably you could set the locale for each call). Some webapps use C in the backend but generally don't deal with the localization at this level.
I'm not saying that C locales aren't bad and limited, I'm saying that it's a compromise that makes some sense. In particular when you're trying to bolt something into an already extremely popular language instead of designing a new thing from the ground up.
Can you imagine the churn if the C standard suddenly introduced a whole new set of string functions just to deal with the locales? Well, you don't really have to imagine, just look at the way it works on Windows with their wide strings.
I'm not saying that C locales aren't bad and limited, I'm saying that it's a compromise that makes some sense. In particular when you're trying to bolt something into an already extremely popular language instead of designing a new thing from the ground up.
Can you imagine the churn if the C standard suddenly introduced a whole new set of string functions just to deal with the locales? Well, you don't really have to imagine, just look at the way it works on Windows with their wide strings.